Marketable Securities - SERP Investments (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020
Net Investment Income [Line Items]
Investment Income (Loss) and Interest Expense	$ 608	$ 1,890	$ 4,360	$ 937
Supplemental Employee Retirement Plan [Member]
Net Investment Income [Line Items]
Investment Income (Loss) and Interest Expense	$ 401	$ 1,200	$ 3,000	$ 1,200

Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities plus amount of the cost of borrowed funds accounted for as interest expense.

No definition available.

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Namespace Prefix:	wmk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration